Rotationally responsive device

ABSTRACT

A rotor is rotationally supported on a housing and spring urged in a first rotational sense. The spring is a multiconvolution resilient steel tape wound on the rotor and disposed between the rotor and the housing in a narrow annular space. Rotation of the housing in a second rotational sense urges the rotor to unwind the spring tape and thereby rotate a predetermined distance. A configuration for a safe and arm mechanism is disclosed.

United States Patent Inventor Fred Krahulec Phoenix, Ariz.

Appl. No. 764,391

Filed Oct. 2, 1968 Patented May 25, 1971 Assignee Motorola, Inc.

Franklin Park, Ill.

ROTATIONALLY RESPONSIVE DEVICE 6 Claims, 3 Drawing Figs.

References Cited UNITED STATES PATENTS 3,013,496 12/1961 Wenig 3,311,060 3/1967 Kelleretal. 102/79 3,320,891 5/1967 Holmes 102/79x 3,479,955 11/1969 Birkigt 102/79x Primary Examirier-Verlin R. Pendegrass Attorney-Mueller & Aichele ABSTRACT: A rotor is rotationally supported on a housing and spring urged in a first rotational sense. The spring is a mu]- ticonvolution resilient steel tape wound on the rotor and disposed between the rotor and the housing in a narrow annular space. Rotation of the housing in a second rotational sense urges the rotor to unwind the spring tape and thereby rotate a predetermined distance A configuration for a safe and arm mechanism is disclosed.

" PATENTED HAY25 l9?! E UL INV FRED KRAH 9 zmw ATTORNEYS ROTATIONALLY RESPONSIVE DEVICE BACKGROUND OF THE INVENTION This invention relates to spin-actuated devices and more particularly to such devices utilizable for safe and arm mechanisms.

The safe handling and proper detonation of artillery shells has been a long problem with many proposed solutions. Many of these solutions require mechanisms of undue complexity which, in effect, reduces the pay load, i.e., the explosive sliding action to rotate a device within the mechanism to an armed position. These devices had the usual setback pin for preventing actuation before firing from an artillery weapon.

The setback forces in some of the and 40 millimeter I weapons could and did on occasion deform the dead soft copper tape such that it could not properly function. The detonation of the shell was then caused by impact rather than by arming the artillery shell in a desired manner. The desired result would then be altered because of the time of detonation was altered.

Also, the frictional engagement between the pedestal and the tape often would give a nonlinear reaction of the dead soft copper tape to the rotational urging altering the time when the projectile was armed. This action would cause defects in the arming of the shell. 1

I The annular space between the pedestal and the outerhousing wall was a distance greater than the diameter of the pedestal. The dead soft copper tape rotated three times for an arming. However, because of imperfections in the tape, the tape could coil up in between the pedestal and the outer housing wall thereby preventing arming. Deformation of the soft copper tape caused. by the setback forces of the artillery weapon also could cause and did cause malfunctions to occur. Another defect in this mechanism is that it could only be used once because of the hardening of the dead soft copper tape. This made it difficult to trouble shoot difficulties in a given design. For example, the center piece of a typical unit was three-eights of an inch diameter and under spin forces the dead soft copper strip would be expanded to a l inch diameter. During the expansion to the larger diameter, there is a rotation of the center bearing about 17 revolutions. A light steel spring was wrapped around the copper coil to prevent it from unwinding until a particular spin rate at which the cen trifugal force overcame the spring tension.

There have been several designs following the above mentioned principles and all these safe and arm devices have the common characteristic of seeking to escape from the so-called safe position in which they are retained by the inner convolute of the unwinder strip. The US. Pat. to Guerne No. 3,076,410 shows an unwinder of the type described above.

Of course, if the rotationally responsive device could be reused they could be used as a limit switch on a governor.

SUMMARY OF THE INVENTION It is an object of the invention to provide a rotationally responsive device having only two parts rotatably movable with respect to a housing and which motion is substantially free of friction.

It is another object of this invention to provide a rotationally responsive device of the unwinding tape type wherein the tape convolutions move radially outward with insubstantial slipping for reducing friction during actuation of the device.

It is a further object of this invention to provide a rotationally responsive device of the unwinding tape type wherein the tape cannot loop upon itself during unwinding.

A feature of the present invention is the disposition of a spring steel tape having several convolutions with one end attached to a center rotatable rotor and an outer end attached to a radially outward housing wall. I

It is a further feature of this invention to have a spring steel tape of several convolutions disposed between a rotor and a housing wall wherein the distance between the rotor outer periphery and the housing wall is not much greater than the radial thickness of the tape. The radial thickness of the annular space is typically less (usually substantially less) than the radius of the center rotor.

Another feature is the rotor rotation is equal to the number of turns or convolutions of the tape multiplied by the rotor rotation of any one of the convolutions; that is, the unwinding of the tape by urging of the rotor due to rotational forces is substantially linear.

According to this invention, there is provided a housing having a base portion rotatably supporting a rotor and having annular walls closely spaced radially outward of the rotor. A multiconvolution spring steel tape is disposed between the rotor and the annular wall having one end affixed to the outer periphery of the rotor and the other end affixed to the annular wall. As the housing is rotated, the rotor urges the spring to unwind one convolution at a time, each outer convolution moving radially outward with minimum friction. The rotor has an arcuate recess preferably of A stop member on the housing extends into the recess and prevents the rotor from rotating beyond a predetermined limit.

Apertures are provided in the rotor, the base portion and the cover portion, The apertures in the cover and base portions are aligned, whereas, the rotor aperture is preferably 180 displaced from the other apertures in the devices in a safe position. Upon actuation, the rotor rotates such that the aperture therein is aligned with the cover and base portion aperturev Typically, the cover portion has a detonator disposed in there, the rotor will carry a lead charge; while a booster is disposed in the aperture of the base portion.

THE DRAWING FIG. 1 is an exploded isometric view of an apparatus used to illustrate the teachings of the present invention.

FIG. 2 is an .enlarged plan view of the FIG. 1 apparatus when the cover portion is formed of transparent material to show internal constructional features. The device is shown in the safe position or unactuated position.

FIG. 3 is a sectional view taken in the direction of the arrows along line 3-3 in FIG. 2 and shows some of the internal constructional features of the illustrated embodiment.

DETAILED DESCRIPTION OF AN ILLUSTRATIVE EMBODIMENT Referring now more particularly to the drawing, like numbers indicate like parts and construction features shown in the various views. The rotationally responsive device includes a cup-shaped housing 10 having a base portion 11 with an upstanding central pin 12 extending along the axis of the housing. Annular walls 13 extend in concentric relationship to pin 12. The upper end of annular walls 13 are adapted to receive cover portion 25 to complete housing 10. A rotor 15' is rotationally disposed about pin 12 which serves as a low friction bearing.

Annular space 16 exists between the outer periphery of rotor 15 and the inner surface of annular wall 13. The radial distance of annular space 16 should never be greater than the radius of rotor 15. The reason for this will be explained later with respect to coiled spring tape 20'.

Rotor 15 has a arcuate recess or slot 17 extending concentric with respect to pin I2. As shown, recess 17 encompasses an arc of 180. Through the use of a stop pin 26 in cover portion 25, which extends into recess 17, the rotation of rotor 15 is limited to 180 as will become more apparent.

Since the device may be used for a safe and arm device in an artillery shell, aperture 18 is formed in rotor 15 for receiving a lead charge (not shown) which when in the armed position 18A can be actuated by a detonator (not shown) disposed in aperture 27 in cover portion 25. This lead charge in turn sets off or detonates a booster charge (not shown) disposed within aperture 19 of base portion 11. Then the regular payload charge (not shown) of the projectile is then in turn detonated by the booster (not shown). The housing may be affixed at the nose of an artillery shell in any known manner such that it rotates therewith to actuate the device from the safe to the armed position. The usual setback safety devices should be provided.

The rotor is one of two parts that rotate with respect to housing 10. The second rotatable part is the multitum or multiconvolution spring steel tape 20 disposed in annular recess or space 16. One end of spring tape 20 is secured in notch 21 of rotor 15. A second and outer end of spring tape 20 is secured in slot 22 of annular wall 13.

In FIG. 2 the device is shown in the safe or unactuated position. Since the cover 25 is shown as being constructed of transparent material, all of the internal parts may be seen in the plane view. In a practical embodiment, the cover portion 25 would be made of metal and one could not see the internal construction. Spring tape 20 has urged rotor 15 clockwise to engage pin or stop member 26 which determines the maximum clockwise rotation of rotor 15. Aperture 18 for containing a lead charge (not shown) is disposed 180 away from apertures 27, 19. The spring tape 20 in this position is wound around the outer periphery of rotor 15.

As the housing 10 is rotated in a counterclockwise sense, as by a projectile, the resultant centrifugal force urges rotor 15 to rotate counterclockwise toward the fully actuated or armed position. In such a movement, aperture 18 is moved from the illustrated position along dotted line 28 to the armed position (dotted lines 18A in FIG. 3) wherein it is aligned with apertures l9 and 27. Recess 17 moves along pin 26 until the counterclockwisemost or armed position is reached whereupon pin 26 again stops rotor 15.

As rotor '15 rotates counterclockwise, the centrifugal force is transmitted to spring 20. Since the end of spring tape 20 is fixedly secured in slot 22 in annular wall 13, it cannot move; therefore, the radially outermost convolution of tape 20 first moves radially outward from the next adjacent convolution. In the illustrated device when such outermost convolution has moved adjacent annular wall 13 the rotor rotated 18. For example, it is desired to move the rotor 180. Since there are 10 convolutions, each convolution moving radially outward corresponds to a rotor rotation of 18. As the counterclockwise centrifugal force continues and increases, the next outermost convolution is next moved radially outward as the rotor continues counterclockwise rotation. It should be noted that the innermost convolutions of tape 20 do not move nor slide with respect to rotor 15 since tape 20 has an innermost end firmly attached to rotor 15, as at notch 21. Therefore, as rotor 15 with the portion of the spring tape 20 securely wound thereto rotates, the outermost convolution first moves radially outward to engage the annular wall 13 or the next adjacent outer convolution which had previously been moved outward. Since the outer convolutions move radially outward due to the centrifugal force, there is no sliding motion therebetween.

Annular wall 13 is radially outward stop for tape 20. It is understood that wall 13 may take any form including wire mesh, axially extending pins, and the like so long as an effective radially outward stop is provided.

It stroboscopic investigations of this invention the housing 10 was rotated by an electric drill, one could see the outermost tape convolutions successively move radially outward without sliding motion. If the rotational velocity was decreased and sufficiently strong spring was used, the spring would cause the rotor to return to the original position. In such action the radially inwardmost convolution would first return to the rotor, then the successively outer convolutions would return to the rotor in opposite sequence to the unwinding.

It is seen that annular space 16 has a relatively short radial dimension. Therefore, the radial excursion, i.e., the radial distance the tape must travel from the unactuated position to the actuated position, is relatively short. This means the tape has very little change in shape. As a result, there are very little internal changes in the tape, i.e., molecular or crystal structure changes, thereby causing very little internal friction. This assists in keeping the response of the spring tape 20 to the rotational urging linear.

The annular space between rotor 15 and annular wall 13 is quite short. This narrow annular space serves to prevent tape 20 from curling on itself as it is unwound. Most readers will have experiences unwinding a coiled tape or wire and noticing that as it is unwound it tends to curl on itself. This curling is caused by the setting of the tape while it is wound in coil form. For reliable operations annular space 16 should be kept small enough to prevent such curling. Actually, the narrower the annular space, the more reliable the operation. This approach is limited by'machining tolerances. For example, if the space between the spring 20 outermost convolution and annular wall I 13 was less than 1,000th inch, there is required a greater number of convolutions to effect a rotation of rotor 15. In other words, the narrower the space 16, the greater the number of turns or convolutions of tape 20 are required to effect a given rotor rotation. Rotor rotational movement is the product of the number of convolutions and the rotational movement permitted by the radial outward movement of each convolution. It is apparent that the smaller this radial outward movement, the smaller the rotational movement of the rotor; hence, the greater number of turns required.

The timing delay of the unwinding of the rotational responsive device is in proportion to the number of convolutions in tape 20. For a given tape, the greater the number of convolutions, the greater the time required to move from FIG. 2 illus trated position to the actuated position indicated by dotted line 18A in FIG. 3.

Because of the low friction in the illustrated embodiment, all of these design parameters may be considered in a straightforward manner. That is, by and large this invention provides an easily designable rotational responsive device because of the low friction involved. In other words, it is essentially a reliable linear rotationally responsive device.

For armament applications it is usual to provide a setback pin such that the mechanism is deactuated until the weapon tires the projectile thereby providing a setback force which withdraws a setback pin for permitting actuation of the rotational responsive device. Also, as the projectile is reaching its maximum rotational velocity it may be desired to lock the rotor in the actuated position. It is well known that as the projectile goes through air the air resistance tends to slow the rotational velocity. In certain instances this rotational velocity may be sufficiently reduced to permit spring 20 to return rotor 15 to an unarmed position. Such locking devices are known and are not discussed for that reason.

The present illustrated embodiment is designed for high spin rate projectiles such as ones that have a spin rate of l2,000 r.p.m. or higher. By adjusting the spring tension to a lower value, lower r.p.m.s may be used to actuate the device. Experience has shown that in most embodiments the higher spin rates cause the device to operate in a reliable manner.

Therefore, there has been illustrated and described a rotationally responsive device which has only two rotatable moving parts with respect to the housing being rotated. The rotor is rotatably mounted on the housing such that there is a low friction support by axial pin 12. The unwinder spring or tape 20 is mounted on the rotor and rotates therewith and unwinds by radially moving convolution by convolution outward to provide a low friction unwinding of the spring.

Iclaim:

l. A rotationally responsive device, including the combinatron,

a housing having a base portion,-an axis andxan annular wall portion concentrically extending around but spaced from said axis, I i

platelike rotor means disposed on saidhousing and rotatable about said axis and having an outer periphery spaced from said wall portion to form an annular space therebetween,

coiled tape means having pluralconvolutions disposed in said annular space and having one end connected to said rotor means at its outer periphery and another end connected to said annular wall portion for yieldably .urg ing said rotor means in a first rotational sense,

said tape means being responsive to rotation of said housing to urge said tape means to unwind and urge rotation of said rotor means in a rotational sense opposite to said first rotational sensefsaid tape means unwinding by moving convolution-by-convolution radially outward with insubstantial rubbing between adjacent convolutions during such action, and said rotor means and a radially inward portion of said tape means being the only parts having rotational motions with respect to said housing.

2. The subject matter of claim 1 wherein said tape means has a total' radial thickness slightly less than the radial thickness of said annular space.

3. The subject matter of claim 1 wherein said annular space has a radial thickness not greater than a radius of said rotor means.

4. The subject matter of claim 3 wherein said tape-means is made of spring steel and has at least 10 convolutions. 5. The subject matter of claim 3 wherein said housing 5 further includes a cover portion closing an end portion of said annular wall portion opposite to said base portion,

a pin extending between said base portion and said cover portion along said axis with "said rotor means rotatably supported by said pin,

an arcuate recess in said rotor means extending concentricto said pin, and

a stop member on one of said portions extending inwardly toward said rotor means-into said recess for limiting the rotational movements thereof .between first and second rotational position.

6. The subject matter of claim 5 wherein said recess extends for for permitting a one-half revolution of said rotor,

said cover portion and said base portion each having aperture means for receiving explosive charges with said apertures being substantially axially aligned,

said rotor means having an aperture located 180 from said 

1. A rotationally responsive device, including the combination, a housing having a base portion, an axis and an annular wall portion concentrically extending around but spaced from said axis, platelike rotor means disposed on said housing and rotatable about said axis and having an outer periphery spaced from said wall portion to form an annular space therebetween, coiled tape means having plural convolutions disposed in said annular space and having one end connected to said rotor means at its outer periphery and another end connected to said annular wall portion for yieldably urging said rotor means in a first rotational sense, said tape means being responsive to rotation of said housing to urge said tape means to unwind and urge rotation of said rotor means in a rotational sense opposite to said first rotational sense, said tape means unwinding by moving convolution-byconvolution radially outward with insubstantial rubbing between adjacent convolutions during such action, and said rotor means and a radially inward portion of said tape means being the only parts having rotational motions with respect to said housing.
 2. The subject matter of claim 1 wherein said tape means has a total radial thickness slightly less than the radial thickness of said annular space.
 3. The subject matter of claim 1 wherein said annular space has a radial thickness not greater than a radius of said rotor means.
 4. The subject matter of claim 3 wherein said tape means is made of spring steel and has at least 10 convolutions.
 5. The subject matter of claim 3 wherein said housing further includes a cover portion closing an end portion of said annular wall portion opposite to said base portion, a pin extending between said base portion and said cover portion along said axis with said rotor means rotatably supported by said pin, an arcuate recess in said rotor means extending concentric to said pin, and a stop member on one of said portions extending inwardly toward said rotor means into said recess for limiting the rotational movements thereof between first and second rotational position.
 6. The subject matter of claim 5 wherein said recess extends for 180* for permitting a one-half revolution of said rotor, said cover portion and said base portion each having aperture means for receiving explosive charges with said apertures being substantially axially aligned, said rotor means having an aperture located 180* from said apertures in said portion when said housing is not rotating such that said tape means is urging said rotor means to engage such stop member with one end of said arcuate recess in said one rotational sense. 